14 
Bismuth  Subiodide. 
Am.  Jour.  Pharm, 
Jan.,  1887. 
crystallization,  but  merely  adhering  moisture  readily  dissipated  by 
proper  drying,  and  hence  cannot  be  considered  as  existing  in  the  state 
of  chemical  combination,  any  more  than,  for  example,  water  contained 
in  improperly-dried  washed  sulphur. 
Returning  to  the  consideration  of  the  oxyiodide  prepared  by  the 
process  given  above  we  find  the  precipitate  to  be  a  fine  brick-red  pow- 
der, odorless,  very  slightly  astringent  in  taste,  showing  extremely  minute 
cubical  crystals,  averaging  about  the  1-32  of  an  inch  in  diameter  when 
magnified  900  diameters ;  insoluble  in  alcohol,  ether  or  chloroform, 
and  evincing  the  general  properties  of  the  compound  of  Messrs.  Wood- 
man and  Tidy.  Now,  as  before  mentioned,  the  chemical  character  of 
this  product  depends  directly  upon  the  quantity  of  acid  used  to  de- 
compose the  potassium  salt.  If  too  much  acid  has  been  used,  the 
filtrate  becomes  red  and  tinges  gelatinized  starch  blue,  and  black  iodide 
is  formed,  resolvable  by  treatment  with  boiling  water  into  the  red 
oxyiodide. 
There  is  an  objection  to  the  acceptance  of  this  "trituration  process," 
as  a  general  one,  while  it  is  extremely  simple,  in  that  it  requires  an 
uncertain  quantity  of  dilute  nitric  acid,  a  very  careful  manipulation, 
and  a  nice  discrimination  as  to  the  exact  point  when  the  decomposition 
is  complete.  Hence  it  would,  probably,  be  considered  only  as  a  ten- 
tative process,  open  for  improvement.  Subsequently,  the  author  suc- 
ceeded in  devising  a  satisfactory  modification  of  the  existing  precipi- 
tation method,  which  would  be  more  practicable,  in  general  employ- 
ment, and  more  capable  of  yielding  a  constant  product  than  that  one. 
The  following  is  the  formula : 
Take  of 
Bismuth  sutraiitrate,  ^iiss,  gr.  xxiv. 
Acid  nitric,  f  ^  iii. 
Hot  water,  f^xii. 
Potassium  iodide,     £xi,  gr.  iii. 
Hot  water,  f^xxviii. 
Dissolve  the  bismuth  salt  in  the  acid  in  a  porcelain  capsule  with  the 
aid  of  heat  and  add  12  fluidounces  of  boiling  water  in  small  portions 
at  a  time,  stirring  after  each  addition.  Then  pour  the  bismuth  solu- 
tion in  the  hot  water,  in  which  has  been  dissolved  the  iodide,  agitating 
it  well  after  each  addition.  Continue  agitating  until  decomposition  is 
complete.  Filter  at  once.  Wash  the  precipitate  with  warm  water, 
dry  and  powder. 
Boiling,  or  nearly  boiling  water,  is  used  to  dilute  the  strong  acid 
